This invention relates generally to gas turbine engines, and more specifically to the repair of turbine blades used in gas turbine engines.
In at least some gas turbine engines, turbine blades used within the engine are cast to an approximate final shape. Portions of the turbine blades, including, but not limited to, a root portion, are then shaped to a final desired form by a shaping technique, such as grinding. The finished turbine blades are assembled into a turbine disk or rotor, such that a “dovetail” formed on each turbine blade engages a complimentarily shaped slot on the turbine disk.
Known turbine blades may be constructed from a high-temperature, high-strength alloy that is adapted to withstand the temperatures and stresses imposed on the parts of a turbine assembly. Because of the high cost of materials, casting operations, and finishing operations, at least some known turbine blades, after being in service, are refurbished to restore the original aerodynamic contours of portions of the blades. At least some known turbine blade repairs, such as those utilized in restoring blade tips, require building up the surface being repaired with a weld bead, and then grinding the surface back to its original contour.
One known technique for building up the blade material by welding is known as superalloy welding at elevated temperatures (SWET) in which tungsten inert gas (TIG) welding is combined with a pre-heating box, referred to as a SWET box. More specifically, in one known method, argon gas is supplied to the SWET box to provide a protective atmosphere for the blades being welded. The argon atmosphere facilitates reducing an amount of contamination within the weld and reducing the amount of cracking within the weld. More specifically, during use a sufficient volume of argon is provided to protect the blade and for good weld quality, and it is not unusual that the argon flow to the SWET box is set excessively high just to facilitate protecting the blades during welding. However, this technique not only unnecessarily increases argon consumption and its associated costs, but also the unnecessarily high gas flow increases the noise level in the area of the SWET box.